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Plane strain test for metal sheet characterization ; ; Habraken, Anne in Key Engineering Materials [=KEM] (2007), 344 This article shows the influence of a plane strain test specimen geometry on the measurable strain field and the influence of free edge effects over the stress computation. The experimental strain field ... [more ▼] This article shows the influence of a plane strain test specimen geometry on the measurable strain field and the influence of free edge effects over the stress computation. The experimental strain field distribution is measured over the whole deformable zone of a plane strain test specimen by an optical strain gauge. The chosen material is the DC06 IF steel of 0.8 mm thickness. The stress field is computed for several geometries at different strain levels by a Finite Element (FE) commercial code (Samcef ®). The results show that the stress field is sensitive to the specimen’s geometry and also to the tested material (strain field behavior is independent of material) and, based on results, an optimal specimen geometry is proposed in order to minimized the stress computation error. [less ▲] Detailed reference viewed: 113 (14 ULg)Multiscale Approaches Duchene, Laurent ; Habraken, Anne in Chinesta, F.; Cueto, E. (Eds.) Advances in Material Forming - Esaform 10 years on (2007) This paper presents a review of the main families of multiscale models. A first group of models is interested in an accurate modelling of the texture induced anisotropy of the material during numerical ... [more ▼] This paper presents a review of the main families of multiscale models. A first group of models is interested in an accurate modelling of the texture induced anisotropy of the material during numerical simulations. The differences between the proposed models are mainly due to different choices concerning the necessary compromise between the importance of the microscopic roots of the model and the maximum admissible computation time. The length scale of the investigated process is also an important parameter. The second group of micro-macro models is based on an analysis of the dislocation densities linked to the plastic deformations. A discussion concerning the past evolution, the recent achievements and the future trends concerning multiscale models is also provided. [less ▲] Detailed reference viewed: 37 (11 ULg)Length changes and texture prediction during free end torsion test of copper bars with FEM and remeshing techniques Duchene, Laurent ; ; Habraken, Anne in International Journal of Plasticity (2007), 23(8), 1417-1438 FEM numerical simulations of the experimental free end torsion tests [Toth, L.S., Jonas, J.J., Daniel, D., Bailey, J.A., 1992. Texture development and length changes in copper bars subjected to free end ... [more ▼] FEM numerical simulations of the experimental free end torsion tests [Toth, L.S., Jonas, J.J., Daniel, D., Bailey, J.A., 1992. Texture development and length changes in copper bars subjected to free end torsion. Textures Microstruct. 19, 245–262] of copper cylindrical bars were analysed in the present study. The self-made Finite Element (FE) code LAGAMINE was used to compute numerical prediction of the Swift effect, i.e. the lengthening of the cylinder during the torsion. The material behaviour was represented by an interpolation law [Habraken, A.M., Ducheˆne, L., 2004. Anisotropic elasto-plastic finite element analysis using a stress–strain interpolation method based on a polycrystalline model. Int. J. Plasticity 20 (8–9), 1525–1560] linked with a Taylor polycrystal plasticity model either based on a strain rate insensitive or a visco-plastic crystal plasticity model. The influence of texture evolution was analysed. A torsion dedicated remeshing technique was developed to allow very large strain simulations. Predicted axial lengthening and predicted textures were compared to experimental measurements. A good agreement was obtained for shear strain up to 2.0. The Swift effect related angular shift of the pole figure maxima from symmetrical orientations was reproduced correctly. [less ▲] Detailed reference viewed: 93 (8 ULg)Finite element study of the effect of some local defects on the risk of transverse cracking in continuous casting of steel slabs Pascon, Frédéric ; Habraken, Anne in Computer Methods in Applied Mechanics & Engineering (2007), 196 This paper introduces a numerical 2.5D model of continuous casting of steel slabs. This model is based on the finite element method and it has been applied to the study of some local defects in a ... [more ▼] This paper introduces a numerical 2.5D model of continuous casting of steel slabs. This model is based on the finite element method and it has been applied to the study of some local defects in a continuous caster, such as partial blockage of nozzles (leading to a local reduction of secondary cooling rate), locking or misalignment of rolls. The purpose of the study was the evaluation of the effect of such defects on the risk of transverse cracking during bending and unbending operations. To do so, the simulation at macro-scale of the complete process has been first performed in standard conditions to get reference values and then each defect has been introduced. Defining two indexes (indicators) of the risk of transverse cracking, it has been possible to classify the defects in terms of risk increase, helping steel producers to focus on the most critical problems. [less ▲] Detailed reference viewed: 82 (6 ULg)Model Identification and FE Simulations Effect of Different Yield Loci and Hardening Laws in Sheet Forming ; Duchene, Laurent ; Bouffioux, Chantal et al in International Journal of Plasticity (2007), 23(3), 420-449 The bi-axial experimental equipment [Flores, P., Rondia, E., Habraken, A.M., 2005a. Development of an experimental equipment for the identification of constitutive laws (Special Issue). International ... [more ▼] The bi-axial experimental equipment [Flores, P., Rondia, E., Habraken, A.M., 2005a. Development of an experimental equipment for the identification of constitutive laws (Special Issue). International Journal of Forming Processes] developed by Flores enables to perform Bauschinger shear tests and successive or simultaneous simple shear tests and plane strain tests. Flores investigates the material behavior with the help of classical tensile tests and the ones performed in his bi-axial machine in order to identify the yield locus and the hardening model. With tests performed on one steel grade, the methods applied to identify classical yield surfaces such as [Hill, R., 1948. A theory of the yielding and plastic flow of anisotropic materials. Proceedings of the Royal Society of London A 193, 281–297; Hosford, W.F., 1979. On yield loci of anisotropic cubic metals. In: Proceedings of the 7th North American Metalworking Conf. (NMRC), SME, Dearborn, MI, pp. 191–197] ones as well as isotropic Swift type hardening, kinematic Armstrong–Frederick or Teodosiu and Hu hardening models are explained. Comparison with the Taylor–Bishop–Hill yield locus is also provided. The effect of both yield locus and hardening model choices is presented for two applications: plane strain tensile test and Single Point Incremental Forming (SPIF). [less ▲] Detailed reference viewed: 88 (11 ULg)Study of a 2024 aluminium rod produced by Rotary Forging Habraken, Anne ; Bouffioux, Chantal ; Carton, Marc et al in Journal of Materials Processing Technology (2007), 184 An investigation of the rotary forging process of a 2024 aluminium rod is summarised. Some dispersion in mechanical properties and chemical composition of the base material is permitted. Samples of two ... [more ▼] An investigation of the rotary forging process of a 2024 aluminium rod is summarised. Some dispersion in mechanical properties and chemical composition of the base material is permitted. Samples of two material batches were selected: one just stays near the upper limit of tolerance and the other has mean properties. Tensile and compression tests confirm the different mechanical behaviours and allow the identification of constitutive laws parameters. Optical metallography after T3 and T10 thermal treatments and differential thermal analysis provide the grain size and precipitation characteristics of each material batch, which explain their different mechanical behaviours. The industrial rod studied is usually forged in two operations: a first forging process, then a T10 thermal treatment followed by a second forging step. Industrial practise shows that manufacturing the rod with one forging step fails. FEM simulations of the process coupled with a fracture criterion confirm the advantage of a two-step process compared to a single forging step. [less ▲] Detailed reference viewed: 123 (18 ULg)Correcting tensile test results of ECAE-deformed aluminium ; ; Habraken, Anne et al in Scripta Materialia (2007), 56(9), 749-752 Performing tensile tests on ECAE material reveals a long post-uniform elongation. In order to calculate correct true stress–true strain diagrams, three different approaches are used: measurements of the ... [more ▼] Performing tensile tests on ECAE material reveals a long post-uniform elongation. In order to calculate correct true stress–true strain diagrams, three different approaches are used: measurements of the actual sample geometry, a neck evolution model proposed by Segal [V.M. Segal, S Ferrasse, F. Alford, Mater. Sci. Eng. A442 (2006) 321–326] and an inverse modelling method by finite element (FE) simulations. [less ▲] Detailed reference viewed: 74 (5 ULg)Numerical study to identify the material parameters of a damage model Schwartz, Renée ; ; Habraken, Anne in Computer Methods in Materials Science (2007), 7(2), 237-242 In the continuous casting (CC) process, transversal cracks happen. This type of macroscopic damage is due to the process loading in the bending and unbending area of the CC line. In order to study this ... [more ▼] In the continuous casting (CC) process, transversal cracks happen. This type of macroscopic damage is due to the process loading in the bending and unbending area of the CC line. In order to study this damage, a 2D model was developed. It simulates the intergranular crack at the mesoscopic level. Already validated for a microalloyed steel with C level < 0.1 wt%, this model must be extended to peritectic and stainless steels. The first step is to identify the model parameters for these grades. The type and the quantity of hot tensile tests required to identify a single set of parameters for the damage law must be determined. So, simulations of hot tensile tests of notched samples are needed. The computed stress and strain histories are applied on the representative mesoscopic cell and the moment of rupture is determined in function of the input parameters. Thanks to inverse modelling, the parameters of the damage law are adapted in order to get one single set of parameters with only two different geometries of notch. [less ▲] Detailed reference viewed: 95 (30 ULg)Validation of a new finite element for incremental forming simulation using a dynamic explicit approach Henrard, Christophe ; Bouffioux, Chantal ; Duchene, Laurent et al in Key Engineering Materials [=KEM] (2007), 344 A new method for modeling the contact between the tool and the metal sheet for the incremental forming process was developed based on a dynamic explicit time integration scheme. The main advantage of this ... [more ▼] A new method for modeling the contact between the tool and the metal sheet for the incremental forming process was developed based on a dynamic explicit time integration scheme. The main advantage of this method is that it uses the actual contact location instead of fixed positions, e.g. integration or nodal points. The purpose of this article is to compare the efficiency of the new method, as far as accuracy and computation time are concerned, with finite element simulations using a classic static implicit approach. In addition, a sensitivity analysis of the mesh density will show that bigger elements can be used with the new method compared to those used in classic simulations. [less ▲] Detailed reference viewed: 96 (16 ULg)A damage constitutive law for steel elevated temperature. Identification of the parameters ; ; Habraken, Anne in International Journal of Material Processing (2007), (1), 23-43 This paper presents a methodology of damage analysis at elevated temperature using the finite element method. Both the model and the methodology to identify parameters are summarized. The mechanical ... [more ▼] This paper presents a methodology of damage analysis at elevated temperature using the finite element method. Both the model and the methodology to identify parameters are summarized. The mechanical properties are established using compression tests at elevated temperature. An elasto-visco-plastic model depending on temperature is identified. A metallographic analysis is used to determine the original size and morphology of the austenitic grains. The experimental damage analyses consist in acoustic tests in order to determine the apparition of the first crack during compression. Finite element simulations of these experiments allow the determination of the damage parameters using a reverse method. [less ▲] Detailed reference viewed: 69 (9 ULg)Springback and Twist Prediction of Roll Formed Parts ; Boman, Romain ; Papeleux, Luc et al in Santos, Abel D.; Barata da Rocha, A. (Eds.) Proceedings of the IDDRG 2006 International Deep Drawing Research Group, Drawing the things to come, Trends and Advances in Sheet Metal Forming (2006, June) In the construction market, Roll Forming is the reference forming process. Numerous parts are achieved in such a way: purlins, steeldecks or suspended ceiling parts are examples of it. Roll Forming is ... [more ▼] In the construction market, Roll Forming is the reference forming process. Numerous parts are achieved in such a way: purlins, steeldecks or suspended ceiling parts are examples of it. Roll Forming is also more and more used in the automotive industry, as it constitutes a good alternative to forming for High Strength Steels. Among the major requirements to obtain a defect-free product are outlined: the accurate geometry of the part, the taking into account of the springback as well as the prediction of twist. Furthermore, the roll forming operation could be only the first forming operation: the part could be curved or locally deep drawn afterwards. FE codes could allow fulfilling these requirements. However, they need significant advances in terms of material model description and numerical development. This paper presents the work done in order to predict the geometry and the behaviour of a roll formed part: First the material is characterized in complex strain paths in order to identify elaborated microstructural model like Teodosiu’s one. This model is able to take into account Bauschinger effect, orthogonal strain paths, isotropic/kinematic hardening. The METAFOR code is then used to have a better understanding of the mechanics of the deformation of the strip during the forming process. Several experimental campaigns were performed on the I-R&D ARCELOR roll forming machine to define a strong database in order to validate the numerical results. The geometry of machine as well as the shape of the channels inside and outside the RF machine were measured. Some experiments were even carried out in order to generate defects like twist in the roll formed profile. [less ▲] Detailed reference viewed: 360 (29 ULg)Finite element simulations of nanoindentation in beta metastable Ti alloys Gerday, Anne-Françoise ; ; et al in Juster, Neal; Rosochowski, Andrzej (Eds.) Proceedings of the 9th International ESAFORM Conference on Material Forming (2006) Nanoindentation is a versatile tool to probe local plastic properties of materials. Finite element (FE) modelling is currently used to identify material data from nanoindentation tests [1-4]. The general ... [more ▼] Nanoindentation is a versatile tool to probe local plastic properties of materials. Finite element (FE) modelling is currently used to identify material data from nanoindentation tests [1-4]. The general ambition of this research is to extract the material parameters describing the response of a new Ti alloy, called Ti-555, in order to perform simulations on representative microscopic cells and guide the optimisation of this alloy. In this paper, the first steps of the identification of the macroscopic flow parameters of the β-phase are described. The nanoindentation tests using a pyramidal Berkovich diamond indenter are performed in the β-phase. The FEM results with different parameters of an isotropic and anisotropic elasto-plastic (EP) constitutive law are analyzed and the predicted shapes are compared to the final shape of the indented material. The FE results very much depend on physical model choices, and cannot rely on an automatic identification approach. [less ▲] Detailed reference viewed: 100 (18 ULg)Out-of-plane displacement derivative measurement: comparison of results obtained by a shearographic interferometer using the separation of the polarization states and the finite element method ; Zhang, Lihong ; Michel, Fabrice et al in Mathieu, P. (Ed.) Proceedings of Photonics North Conference 2006 (2006) An original experimental setup for shearography with metrological applications is presented herein. The simplicity and the efficiency of the setup are provided by a shearing device, a prism that separates ... [more ▼] An original experimental setup for shearography with metrological applications is presented herein. The simplicity and the efficiency of the setup are provided by a shearing device, a prism that separates the TE and TM polarization modes with a coating and a thin glass plate attached on its face. The temporal phase shifting method is applied through the use of a liquid crystal variable retarder. The use of this shearing device enables an in-line and almost-common path configuration for the shearing interferometer, a path that leads to high stability of the interferometer and a low sensitivity to external disturbances. In order to prove the efficiency and the accuracy of this speckle shearing interferometer, the out-of-plane displacement derivative relative to the shearing interferometry direction of a centrally loaded steel plate has been measured by the shearographic interferometer and then compared with the out-of-plane displacement derivative computed from the displacement field provided by the finite element method. The results are in good agreement. [less ▲] Detailed reference viewed: 76 (16 ULg)Numerical study of the fatigue crack in welded beam-to-column connection using cohesive zone model Lequesne, Cédric ; Plumier, André ; Degée, Hervé et al in Proceedings of the International Conference on Fracture and Damage Mechanics V (2006) The fatigue behaviour of the welded beam-to-column connections of steel moment resisting frame in seismic area must be evaluated. The cohesive zone model is an efficient solution to study such connections ... [more ▼] The fatigue behaviour of the welded beam-to-column connections of steel moment resisting frame in seismic area must be evaluated. The cohesive zone model is an efficient solution to study such connections by finite elements. It respects the energetic conservation and avoids numerical issues. A three-dimensional cohesive zone model element has been implemented in the home made finite element code Lagamine [1]. It is coupled with the fatigue continuum damage model of Lemaître and Chaboche [2]. The cohesive parameters are identified by the inverse method applied on a three points bending test modelling. [less ▲] Detailed reference viewed: 73 (15 ULg)Inhomogeneous and anisotropic deformation behavior and strain hardening of ultrafine-grained aluminium by ECAP ; ; Habraken, Anne et al in Zhu, Y. T.; Langdon, T. G.; Horita, Z. (Eds.) et al Proceedings of the Ultrafine Grained Materials IV Conference (2006) Hot-rolled AA1050 commercial pure aluminum was deformed by ECAP (Equal Channel Angular Pressing) at room temperature following route BC for 8 passes. Mechanical testing at room temperature on both hot ... [more ▼] Hot-rolled AA1050 commercial pure aluminum was deformed by ECAP (Equal Channel Angular Pressing) at room temperature following route BC for 8 passes. Mechanical testing at room temperature on both hot-rolled aluminum and aluminum after ECAP consisted of uniaxial tension, axisymmetric compression and shear by torsion. The phenomenological Hill’s criterion identified from texture data accounts for the observed tension-compression asymmetry due to ECAP and predicts torsion yielding close to measurements. FE simulations of the compression tests are performed with a Hill model or a Minty micro-macro model and coupled with an isotropic Voce saturation hardening law. These simulations compute the inhomogeneous behavior due to barreling, the observed sample anisotropy and the force-displacement curve. Comparisons of numerical and experiments results provide a first identification of the hardening parameters and the friction coefficient during compression tests. [less ▲] Detailed reference viewed: 105 (2 ULg)Prediction of deformation textures in zirconium based on a simplified modelling of grain interaction ; ; Habraken, Anne in Khan, A. S. (Ed.) Proceedings of the Plasticity Conference 2006 (2006) The goal of this study is to apply a “multisite” crystal plasticity model to the prediction of texture evolution in zirconium deformed at high temperature. The model under consideration is an extension of ... [more ▼] The goal of this study is to apply a “multisite” crystal plasticity model to the prediction of texture evolution in zirconium deformed at high temperature. The model under consideration is an extension of the elastic-viscoplastic “multisite model” proposed by Delannay et al. [2005] which has been adapted to account for a new type of grain interaction (Van Houtte et al. [2005]). Predictions of the model are compared to experimental data. Two forming processes are considered: sheet rolling (Lebensohn et al. [1994]) and the torsion of a cylindrical bar (Sanchez et al. [2001]). [less ▲] Detailed reference viewed: 23 (1 ULg)Analysis of speckle patterns for deformation measurements by DIC ; ; et al in Slangen, Pierre; Cerruti, Christine (Eds.) Proceedings of SPIE Vol. 6341 (2006) Digital Image Correlation (DIC) – also referred to as white light speckle technique – is an optical-numerical full-field measuring technique, which offers the possibility to determine in-plane ... [more ▼] Digital Image Correlation (DIC) – also referred to as white light speckle technique – is an optical-numerical full-field measuring technique, which offers the possibility to determine in-plane displacement fields at the surface of objects under any kind of loading. For an optimal use of the method, the object of interest has to be covered with a speckle pattern. The present paper studies the efficiency of a random speckle pattern and its influence on the measured in-plane displacements with respect to the subset size. First a randomly sprayed speckle pattern is photographed three times. Each picture is taken with a different zoom, yielding three speckle patterns, which are different by the size of the speckles. Secondly a number of speckle patterns are generated numerically using a given speckle size and image coverage. Subsequently, each speckle pattern image undergoes a numerically controlled deformation, which is measured with digital image correlation software. Both imposed and measured displacements are compared and it is shown that the size of the speckles combined with the size of the used pixel subset, clearly influences the accuracy of the measured displacements. Furthermore it is shown that it is possible to create an optimal speckle pattern when a given subset size is chosen. [less ▲] Detailed reference viewed: 196 (7 ULg)Comparison between homogeneous and heterogeneous field information for plastic material identification ; ; et al in Grédiac, Michel; Huntley, Jonathan (Eds.) Proceedings of Photomecanics Conference 2006 (2006) The accuracy of a Finite Element Simulation for plastic deformation strongly depends on the chosen constitutive laws and the value of the material parameters within these laws. The identification of those ... [more ▼] The accuracy of a Finite Element Simulation for plastic deformation strongly depends on the chosen constitutive laws and the value of the material parameters within these laws. The identification of those mechanical parameters can be done based on homogeneous stress and strain fields such as those obtained in uniaxial tensile tests and simple shear tests performed in different plane material directions. Another way to identify plastic material parameters is by inverse modeling of an experiment exhibiting a heterogeneous stress and strain field. Experimental forces and strains are in this case compared to the simulated ones and it is tried to reduce the difference in a least-squares sense by optimizing the model parameters. The optimization technique used is this case is gradient based, which means that at every iteration a sensitivity calculation has to be performed in order to indicate the direction in which the parameters are to be identified. The basic principle of the inverse modeling procedure as it is used for parameter identification is the generation of a complex and heterogeneous deformation field that contains as much information as possible about the parameters to be identified. One way of obtaining such a non-homogeneous deformation is by altering the geometry of the specimen for a uniaxial test. Another possibility is to make the loading conditions more complex. In this paper both options are actually combined by using a biaxial tensile test on a perforated cruciform specimen. In the present paper, the work hardening of the material is assumed to be isotropic and it is described by a Swift law. The yield locus is modeled by the anisotropic Hill48 criterion. A comparison is made between the identification of the Hill48 parameters based on the one hand on the Lankford coefficients [1] and on the inverse modeling of a biaxial tensile test on the other hand [less ▲] Detailed reference viewed: 52 (2 ULg)Identification of yield locus parameters of metals using inverse modeling and full field DIC ; ; et al in Proceedings of the 7th national congress on theoretical and applied mechanics (2006) The basic principle of the inverse modeling procedure as it is used for parameter identification is the generation of a complex and heterogeneous deformation field that contains as much information as ... [more ▼] The basic principle of the inverse modeling procedure as it is used for parameter identification is the generation of a complex and heterogeneous deformation field that contains as much information as possible about the parameters to be identified. One way of obtaining such a non-homogeneous deformation is by making the geometry of the specimen less regular. Another possibility is to make the loading conditions more complex. In this paper both options are actually combined by using the concept of a biaxial tensile test on a perforated cruciform specimen. In the present paper, the work hardening of the material is assumed to be isotropic and it is described by a Swift law. The yield locus is modeled by the anisotropic Hill48 criterion. The optimization technique used is a constrained gradient based Newton-type routine, which means that in every iteration step, a sensitivity calculation has to be performed in order to indicate the direction in which the parameters are to be optimized. The functional to be minimized is a least-squares expression of the discrepancy between the measured and the simulated strain fields at a certain load. The numerical routines as well as the identification results of the different parameters, based on simulated strain fields, are discussed. [less ▲] Detailed reference viewed: 51 (3 ULg)Identification of hardening behavior using inverse modeling and image correlation ; ; et al in Proceedings of the SEM annual conference and exposition 2006 (2006) The basic principle of an inverse modeling procedure as it is used for parameter identification, is the generation of a complex and heterogeneous deformation field that contains as much information as ... [more ▼] The basic principle of an inverse modeling procedure as it is used for parameter identification, is the generation of a complex and heterogeneous deformation field that contains as much information as possible about the parameters to be identified. One way of obtaining such a non-homogeneous deformation is by making the geometry of the specimen less regular. Another possibility is to make the loading conditions more complex. In this paper both options are actually combined by using a biaxial tensile test on a cruciform specimen in order to identify the parameters of a Swift isotropic hardening law. The yield criterion is modeled by the isotropic Von Mises criterion. The optimization technique used is a constrained gradient based Newton-type routine, which means that in every iteration step, a sensitivity calculation has to be performed in order to indicate the direction in which the parameters are to be optimized. The functional to be minimized is a least-squares expression of the discrepancy between the measured and the simulated strain fields at a certain load. The numerical routines as well as the identification results, based on simulated strain fields, are discussed. [less ▲] Detailed reference viewed: 39 (3 ULg) |
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